/Engine/Plugins/Online/OnlineServices/Source/OnlineServicesCommon/Public/Online/OnlineAsyncOp.h
TOnlineAsyncOpCallableTraitsHelper2< TResultType, OpType & >TOnlineAsyncOpCallableTraitsHelper2< TResultType, OpType &, TParamType >
template<typename... Params> struct TOnlineAsyncOpCallableTraitsHelper2